In the frozen food field, attempts have been made to package fresh, edible plant products, such as herb, fresh fruit and fresh vegetable products so that the desirable qualities of the fresh products are maintained. In particular, the art has recognized the desirability of preparing a product that would maintain quality, flowability and easy handling characteristics for long periods of time at frozen temperatures as well as when the product is repeatedly thawed and refrozen or when the product is left in a refrigerated state (approximately 40.degree. F. or about 4.degree.-5.degree. C.) for several days or longer. In particular, the art has recognized the desirability of preparing a product that would maintain quality, consistent supply, easy handling characteristics and portion control year round thus enabling food producers, food merchants, or restaurants to stock such product, in particular, the aromatic products for sale to consumers while reducing losses due to spoilage, waste or deterioration. Since many of the edible plant products including herbs, fruits and vegetables valued for use in foods are, for climatic reasons, generally only available regionally and/or seasonally, the art has recognized a need for products that could be pre-processed to eliminate waste, stored in a frozen state to preserve fresh flavor, color and overall appearance, and also maintain flowability and ease of handling in the frozen state.
In many of these products some of the properties that cause consumers to value the fresh character of these food products are difficult to maintain for extended periods. This problem is especially acute with fresh leafy plants which often may contain their flavor and aroma components in discrete oil or flavor glands. Such plants are typically classified as herbs, sometimes more particularly as aromatic herbs. Accordingly, it would be desirable to preserve the color, flavor, aroma and overall natural or comminuted appearance of fresh herbs without resorting to chemical additives, special types of packaging or packaging equipment while providing an extended shelf-life for the packaged product. The technique of freezing plant products has been utilized for many years as a method of preserving fresh character, flavor and appearance. However, inherent enzymatic activity in biological materials which is somewhat active in the frozen state and upon thawing can lead to severe degradation of flavor, color and appearance. To overcome this problem, the plant material is usually blanched to inactivate enzymes prior to further processing and preservation by freezing. Blanching in water partially cooks the product which can lead to loss of fresh flavor and appearance. Attempts have been made to maintain fresh appearance by adding components to the blanched product such as sugars, salt and food acids.
Blanching herbs results in a substantial loss of the flavor and aroma components. Accordingly several approaches have been adopted to avoid blanching. Most of these involve the use of oils, salts, acids and the like coupled with freezing. These techniques suffer from several serious deficiencies. The above additives may cause flavor, color and texture changes as well as causing undesirable ingredients to be added to the ingredient declaration. Also, to achieve a free flowing product, the expensive individual quick freezing technology (IQF) must be used. While IQF technology provides an initially free-flowing product, the product will lose its free-flowing characteristics when thawed and refrozen. Techniques using oils such as olive oil impart their own characteristic flavor to the product. Another deficiency is that the products generally do not have good integrity upon thawing; that is, the herb pieces tend to disintegrate upon use thereby losing their desirable visual impact. Also, some of these techniques result in undesirable color changes which precludes the use of such products where it is desired to use the herbs to achieve a visual impact. Lack of piece identity and product color changes also create an undesirable consumer reaction if the products are sold in transparent containers and upon use.
The prior art contains numerous descriptions of processes for preparing frozen food or preserved food products using sugar, see for instance U.S. Pat. Nos. 5,110,609, 5,073,400, 4,478,868, 4,447,460, 4,390,550, 3,219,461 and U.K. patent 2,225,521. However, none of these processes are concerned with the unique problems encountered in freezing herbs. U.S. Pat. No. 5,093,145 teaches a process for processing herbs using chemical enzyme-blocking agents, but it does not provide a product having freeze-thaw stability and, in particular, free-flowing properties.
Techniques to solve the foregoing problems by preserving herbs by improved dehydration techniques have not been successful. EP 285,235 describes a dehydrated herb product containing glycerol which retains most of the color and flavor of fresh herbs. Unfortunately, the product has an atypical surface texture, limited ambient shelf life, an excessive sweetness, and upon long term storage, separation of the glycerol from the herbs occurs. Also, because glycerol is a chemical additive, the product cannot be marketed or sold as free of artificial ingredients. A technique which overcomes the deficiencies in EP 285,235 is described in our application S.N. WO 9210946, filed Jul. 9, 1992. This technique produces a dehydrated herb having superior organoleptic properties to ordinary dehydrated herbs. The process of S.N. WO 9210946 comprises a combination infusion, osmotic dehydrating and blanching step using an osmotic solution containing an osmotic agent which infuses into and osmotically dehydrates the herb. The infused product is then dried to a low moisture level, typically below 6% moisture to form an amorphous coating which encapsulates the oil sacs or glands, and the dehydrated product recovered. However, a need continues to exist for a preserved herb product having organoleptic properties closer to fresh herbs than can be achieved by the process of S.N. WO 9210946.
A need also exists for a frozen herb product which retains the structural integrity, color and organoleptic properties of fresh herbs. A need, in particular, exists for a frozen herb product which is free-flowing even after undergoing freeze-thaw cycles.